President Trump and North Korea’s Kim Jong Un participated in a document signing Tuesday afternoon in Singapore.

Details of what the two world leaders signed were not immediately known, but Trump called the document “pretty comprehensive.”

Observers called the paperwork a “declaration” regarding denuclearization, as well as a “letter of intent,” full of promises by the American president to take care of a “very dangerous problem.” Jong Un projected “major change for the world.”

Trump also said the meetings with Kim had gone “better than anybody could have expected.”

Earlier in the day in a staged ceremony on a Singapore island, Trump and Kim were seen clasping hands before a row of alternating U.S. and North Korean flags, holding a one-on-one meeting, additional talks with advisers and a working lunch.

After the lunch, Trump announced the signing ceremony but provided no details, saying only: “We’re going to be announcing that in a couple of minutes.”

At a meeting that could chart the course for historic peace or raise the specter of a growing nuclear threat, both leaders expressed optimism. Kim called the sit-down a “good prelude for peace” and Trump pledged that “working together we will get it taken care of.”

For all the upbeat talk, it was an open question what, if any, concrete results the sit-down would produce. In advance of their private session, Trump predicted “tremendous success” while Kim said through an interpreter that “we have come here after overcoming” obstacles.